Closed-chest electrode-catheter technique for His bundle ablation in dogs

Area of Science:

• Cardiovascular Research
• Electrophysiology

Background:

• Complete atrioventricular (AV) block impairs heart rate regulation.
• Existing models for studying AV block may lack stability or specific functionalities.
• Understanding heart rate control mechanisms during AV block is crucial for therapeutic development.

Purpose of the Study:

• To develop and validate a reliable method for inducing complete AV block in a canine model.
• To assess the characteristics of induced AV block and its response to physiological stimuli.
• To evaluate the potential of this model for research requiring controlled heart rates.

Main Methods:

• A modified quadripolar electrode catheter with insulated distal surface was used in 10 dogs.
• Direct-current electrical discharge was applied to induce AV block after His bundle potential recording.
• Physiological responses, including cycle length changes with exercise and response to beta-blockade and overdrive pacing, were monitored.
• Histopathological examination was performed to assess for tissue damage.

Main Results:

• Complete AV block was successfully induced in 9 out of 10 dogs.
• Induced AV block was characterized by broad QRS complexes without His bundle deflections.
• Heart rate during AV block showed a decrease after exercise, which was attenuated by beta-blockade.
• Overdrive pacing led to temporary pacemaker suppression.
• No myocardial or valvular damage was observed.

Conclusions:

• The described technique provides a stable and reproducible animal model for complete AV block.
• This model is suitable for experimental investigations requiring controlled heart rate conditions.
• The method may offer potential applications for patients with tachycardia necessitating His bundle ablation.